Inhibitory Effects of Wa-Kocha (Japanese Black Tea) on α-Glucosidase Activity and Postprandial Blood Glucose Elevation

Abstract

  This study aimed to investigate the α-glucosidase inhibitory effect and postprandial blood glucose level suppressing effect of Japanese black tea. Of the 19 Japanese black tea species, 15 showed an inhibition rate of α-glucosidase activity of ≥ 50%. A positive correlation was observed between the inhibition rate of α-glucosidase activity and the suppressive effect on postprandial blood glucose levels. Additionally, no significant difference was observed in the postprandial blood glucose levels of 29 healthy women after consuming Japanese black tea and water. However, among the 15 subjects with tendencies for postprandial blood glucose elevation, the results demonstrated significantly lower blood glucose levels 30 minutes after a meal, when levels typically peak, when consuming Japanese black tea compared to water. These findings indicate that Japanese black tea has an inhibitory effect on α-glucosidase activity. Furthermore, drinking Japanese black tea with a meal has the potential to suppress the increase in postprandial blood glucose levels in individuals prone to elevated blood glucose levels.